Don't want to belabor this point too much, but there were several times in Clark County when I was supervising an election site where someone  came to vote in person, but had already "voted" because someone (unbeknownst to the voter) had requested an "absentee ballot".  When I was on the job, the remedy to that situation was to allow the voter to sign an affidavit affirming they had not voted and that they were aware that double voting was a felony.  With said affirmation signed, the voter was permitted to vote.  Supposedly, the affirmation was SUPPOSED to cancel the prior vote in favor of the in-person vote.  Supposedly...(what a great way to cheat...ya think??)